Should recessions of the medial recti be graded from the limbus or the insertion?

In a series of 27 patients who were operated on for esotropia, we compared patient response to surgery and the distance the medial recti were recessed from the insertion and corneoscleral limbus. We found a much more significant correlation between the response and the amount the muscles were recessed from the insertion than from the corneoscleral limbus. Using partial correlation coefficients, we found that when we corrected for the amount of recession from the insertion, there was not a significant correlation between the response to surgery and the amount the muscles were recessed from the corneoscleral limbus. This suggests that the apparent correlation between the response to surgery and the amount of recession from the corneoscleral limbus simply reflects that the greater the recession from the corneoscleral limbus, the farther the muscle is likely to end up posterior to the insertion.